By Ashay Abbhi
The pursuit to resolve the challenges in the Indian renewable energy sector has given rise to many innovative solutions, especially in the wind and solar energy segments. The complementarities of the two technologies harnessed through hybrid power plants, have emerged as a solution. Coupled with energy storage, these solar-wind hybrid plants can seamlessly supply power round the clock with much greater control as compared to plants without storage. In light of the country’s need for better grid integration, the recently released National Solar-Wind Hybrid Policy by the Ministry of New and Renewable Energy (MNRE) permits the addition of battery storage to any solar-wind hybrid power plant. It is interesting to note that while the initial investment for solar-wind hybrids plus storage will be much more than that for only solar plus storage plants, the resulting higher quantum of energy generated and availability of better quality power could greatly enhance the cost benefits of the storage system.
The analysis of solar-wind hybrid plus storage in comparison to only solar plus storage power generation systems highlights a significant cost benefit for the former. With hybrids, the added wind component has a significant impact on savings in terms of a reduction in the size of the storage component. Assuming that a typical solar energy plant generates power for eight hours a day, storage would be required for 16 hours in order to make electricity available throughout the day. Adding a wind energy component to this system brings the typical daily generation up to 16 hours (wind energy generation is more effective during the evening and night). As a result, the storage component would be required only for eight hours a day, thereby reducing the cost of storage by about half of that of only a solar plus storage system. Moreover, as solar-wind hybrids are more suitable for states with high wind speeds, the wind energy generator there would be more efficient, further reducing the size of the solar and storage components.
Energy storage essentially helps in decreasing the variability of renewable energy generation. Therefore, the complementarities achieved by using solar and wind energy together are further enhanced when feeding power into the grid. For decentralised systems, storage acts as a regulating mechanism that helps control the storage and release of power according to the time of day. For instance, for a solar-wind hybrid microgrid installed at a remote off-grid location, the storage component can store power during peak generation and low demand (typically during the day) and provide power during peak demand (from evening to night), especially on cloudy or low wind days.
The biggest challenge in the adoption of energy storage has been its high cost. However, with the proliferation of electric vehicles, the use of storage technologies is likely to go up, driving down costs in the process. Globally, renewable project developers have already started experimenting with storage-based hybrids. The inclusion of storage capacity in recent government tenders in India is also a testimony to its practicality and cost benefits. The Andhra Pradesh government is planning to release a tender for a hybrid plus storage project with 120 MW of solar, 40 MW of wind and 20-40 MWh of storage in 2018-19. Meanwhile, Kerala’s Agency for Non-Conventional Energy and Rural Technology has been working on a pilot project to set up a plant with 3 MW of solar and 4 MW of wind capacity along with battery storage.
In January 2018, the Solar Energy Corporation of India (SECI) invited expressions of interest to develop a 160 MW solar-wind hybrid plus storage project in Ramagiri district of Andhra Pradesh. In May 2018, SECI announced a plan to tender 2.5 GW of solar-wind hybrid projects, with a specific component for installing any energy storage technology with the plants.
Challenges and outlook
The policy infrastructure for solar-wind hybrids plus storage is yet to be put in place. However, it is expected that more than the policies, it will be the falling cost of storage that will drive the market. Currently, storage component costs present the greatest hurdle in making the technology attractive. The physical space required by energy storage due to its bulkiness is another challenge. In a country like India, where land accounts for 10 per cent of the cost and 90 per cent of the problems, space constraints may hamper the growth of the storage market. Amidst such challenges, it is safe to assume that it will be a while before the hybrid plus storage market takes off. The benefits of the technology outweigh the challenges by a large margin. While it may take time to grow, solar-wind hybrids plus storage are being pushed as a technology of the future. There are several global examples and best practices for developers in India to follow to create demand, which would lead to a reduction in storage costs and further uptake of the technology.